Method of manufacturing a container by casting and working



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METHOD OF MANUFACTURING A CONTAINER BY CASTlNG AND WORKING Dec. 12, 1967 Filed Oct. 1 1963 Dec. 12, 1967 A. J. KLEIN 3,357,095

METHOD OF MANUFACTURING A CONTAINER BY CASTING AND WORKING Filed Oct. 1, 1963 5 Sheets-Sheet 2 w j 5 /lfi //Z @a 02 /7Z w v -/7/ /7/ w M l! V)? J I INVENTOR.

141554 7 Tiff P4 KZf/A/ Dec. 12, 1967 A J. KLEIN 3,357,095

METHOD OF MANUFACTURING A CONTAINER BY CASTING AND WORKING 3 Sheets-Sheet .5

Filed Oct. 1, 1963 If Z251.

ATTUR/Vfy simplified with a two-piece United States Patent 3,357,095 METHOD OF MANUFACTURING A CONTAINER BY CASTING AND WORKING Albert Joseph Klein, Arlington Heights, 11L, assignor to American Qan Company, New York, N.Y., a corporation of New Jersey Filed Get. 1, 1963, Ser. No. 313,000 12 Claims. (Cl. 29-528) This invention relates to the method of manufacturing a thin-walled one-piece metal container and the container produced thereby, more particularly it relates to a onepiece metal container which is manufactured by molding a shallow cup from molten metal and thereafter ironing the side wall or body of the cup in order to produce a one-piece metal container whose end and body have substantially the same thickness.

In the canning of many products, especially those canned under high pressure such as aerosols, the use of a twopiece can has been increasing in usage. This two-piece can comprises a body and one integral end and an opposite end affixed thereto, rather than the conventional threepiece can which is made up of a body and two ends secured to the end openings of the body.

It is readily apparent that having one end and the body made from a single piece of metal, thereby eliminating the joining of this end to the body, will produce a higher strength container. In addition, a number of individual manufacturing operations and the complexity of the end manufacturing and securing process may be considerably container.

Processes that have most generally been utilized in manufacturing metal containers having an integral body and end are drawing, impact extrusion and drawing and ironing. In each of these methods of manufacturing metal containers a preform must be utilized. In the cases of drawing and drawing and ironing, this preform is generally rolled sheet metal, while for impact extrusion the preform is generally a cast or punched metal slug.

Drawing and ironing devices and processes have already been proposed and used for forming tubular containers from a flat blank in a continuous stroke, particularly containers made from aluminum or other soft homogeneous metals. Generally, the procedure used involves drawing the blank into cup form in the usual manner,

after which, in the same continuous stroke, the punch carries the drawn cup through a series of ironing dies, each slightly smaller in diameter than the preceding die and all being slightly smaller in diameter than the drawing die.

As drawn, the cup usually has bottom and side wall thicknesses essentially equal to the thickness of the flat blank. The ironing thins the side wall of the drawn cup and forces the metal back, thereby increasing theheight of the container. Additional ironing steps may be added to achieve a desired body wall thickness and container height.

However, the container produced by this drawing and ironing method has a body wall substantially thinner than the bottom, the bottom thickness being substantially the same as the original thickness of the flat blank. In many instances it is desirable to be able to vary the thickness of bottom in relation to the side wall, for example to make the bottom and side wall of equal thickness and thereby effect a saving of material.

As used herein, the term ironing refers to the operation wherein the side wall of a cup is elongated by reducing its thickness with no appreciable reduction in the diameter of the cup. It is generally accomplished by placing the cup on a closely fitting punch or mandrel and forcing the cup and mandrel through an ironing, or

reducing die or series of dies whose diameter is slightly less than the outer diameter of the cup, thereby forcing the excess metal back and producing a longer, but thinner side wall.

It has long been desired to eliminate the use of metal sheet for the manufacture of containers by drawing and ironing and, instead, to manufacture the container directly from molten metal without the necessity for going through the expensive procedure of rolling metal billets to sheet for the subsequent manufacturing of containers.

It is therefore an object of the present invention to provide a container having an integral body and end.

Another object is to provide a container having an integral body and end, the thickness of which end may be varied to be equal to, greater than, or less than the thickness of the body.

An additional object is to provide a method of manufacturing a metal container directly from a pool of molten metal.

A still further object is to provide a simple and inexpensive method of manufacturing a one-piece cupshaped container directly from molten metal.

Numerous other objects and advantages of the invention will be apparent as it is better understood from the following description which, taken in connection with the accompanying drawings, disclose a preferred embodiment thereof.

The above objects are accomplished in the present invention by molding a cup-shaped blank from a pool of molten metal, the bottom of the blank being relatively thin as compared with the thickness of the blank side wall. The molded metal blank has an as-cast grain structure. After molding, the bottom of the blank is placed over and in alignment with a female ironing die assembly. Then a punch, aligned with the die assembly, is brought into the cavity of the blank and forces the blank through the die assembly whereby the side wall of the blank is elongated and substantialy reduced in thickness without any substantial change in the thickness of the bottom, thereby producing a cup-shaped, one-piece metal container with a relatively thin body wall and end of substantially the same thickness.

Referring to the drawings:

FIGS. 1 through 4 are cross-sectional views showing the sequence of operations for forming a cup from a bat-h of molten metal by one form of apparatus;

FIG. 5 is a view of the pipe orifice taken substantially along the line 55 of FIG. 1;

FIGS. 6 through 8 are schematic views, partly in section, of a modified apparatus for performing the invention;

FIG. 9 is a sectional view of the ironing apparatus;

FIGS. 10 through 12 are fragmentary views, similar to FIG. 9, showing a cup being formed to a desired container configuration; and

FIG. 13 is a perspective view, partly in section, showing a molded and ironed container.

As a preferred or exemplary embodiment of the instant invention, a cup-shaped mold, generally designated 12, comprising two sections 14 and 16 which form the body of the mold 12 and are generally symmetrical in shape, and an end 18, is placed over and slightly into a pool 20 of molten aluminum held within a suitably heated pot 22 (FIG. 1).

A skirt 23 of the sections 14 and 16 is positioned below the surface 24 of the molten pool 20. If desired a separate ring may be used below the molten metal surface 24 and the skirt 23 may be positioned so it is in contact with the surface 24 and not into the metal pool 20.

The mold 12 is mounted on a vertically movable shaft 25 which is driven by suitable means, not shown. At the juncture of the sections 14 and 16 with the end 18, a

series of vents 26 are provided to exhaust the air within the mold 12 during the molding operation. A suitable material such as aluminum or silicon carbide, is used to make the mold 12.

Below and substantially centered beneath a cavity 2,8 of he m d 2 s a holl P pe 30 f om wh ch n oxi izins se y be em ed du ing meldius- Au orifice 31 (FIG. of the pipe 30 contains a plurality of small holes 32 through which the gas passes. It is preferred that the orifice be made of a non-wetting material that will also not be excessively corroded by the molten aluminum. A ng the m t rial th may be u ed ar a und m a d silicon carbide. A suitable source, not shown, of oxidizing gas, such as a high pressure tank, is provided.

In :the molding process, as shown in FIGS. 3 and 4, a bubble 33 of oxidizing gas is emitted from the orifice 31 of the pipe 30, the orifice 31 being below the surface of the molten aluminum 20. As the bubble 33 rises, a layer 36 of semi-solid aluminum, generally in the solid plus liquid range, forms upon the bubble 33.

During this blow molding operation, the molten pool 20 is maintained at a temperature slightly over the liquidus temperature, i.e. lO-50 F. This liquidus temperature will, of course, vary somewhat depending upon the particular aluminum alloy utilized. Among the numerous aluminum alloys that have been found usable in this process are 2025, 2024, 3003, 5056 and B750.

The oxidizing gas which forms the bubble 33 is preferably a mixture of nitrogen and oxygen, Although the oxygen content may be from 1 to 99%, it is preferred that the gas contain 2% oxygen and 98% nitrogen. The pressure of the gas is maintained between 4.0 and .60 mm. of mercury.

As the bubble 33 continues to rise and is made to expand within the mold cavity 28, the aluminum layer 36 contracts the inner surface 38 of the cavity 28 and freezes solid. As the metal further solidifies throughout its crosssection, it assumes the form of a cupshaped blank d0 having a generally smooth inner and outer surface on its side wall .42 and bottom 44.

Once the cup-shaped blank 40 has completely solidified, the mold 12 is removed from the pot ,22 and the blank 40 is separated from the mold 12.

In some cases where precise control of the thickness of the blank side wall 42 and bottom 4,4 are desired, the temperature of various areas of the mold 12 may he controlled by external heating or cooling means. In the present case the blank 40 is molded so that its bottom .44 is thinner than the side wall 42, for purposes that will be more fully explained hereinafter.

As molded, the aluminum metal is in a chill .cast condition exhibiting generally very small grains in the bottom 4 i he r n s ze n the s de Wa l 2 increasin wards the open end 45 of the blank 40. When the blank 40 is made from 2025 aluminum alloy is generally has a Rockwell 15.T hardness of about 67, an ultimate tensile strength of about 29,600 p.s.i., and a yield strength of about 21,500 psi.

In another form of the invention, as shown in FIGS. 6-8, a. pool 50 of molten aluminum within a suitable pot 52 is provided. Above the pool 50 is positioned a tubular mandrel 5.4 Whose side wall 56 and bottom 58 are sub.- stantially normal to each other and meet in a chamfered or curved portion 60.

It is preferred that the mandrel 54 be internally cooled by some suitable means, such as a liquid coolant. The coolant is supplied from a suitable source, such as a compressor (not shown) through a conduit 62, which also serves to return the heated liquid to the compressor for cooling. The mandrel 54 may either be hollow, and cooled en masse, or internal piping may be used to control the temperature of different sections of the mandrel 54. It is preferred that the side wall 56 be maintained at a lower temperature than the bottom during the molding operation.

Cil

As in the blow molding process described hereinbefore, the mandrel 54 is preferably made of a material that will not be excessively corroded by the molten aluminum metal.

With the molten aluminum pool 50 in the liquid phase, the mandrel 54 is immersed in the pool 50 to a predetermined depth. During immersion, the mandrel 54 is internally cooled substantially below the solidus temperature of the molten aluminum alloy. Thus a solidified 'mass 64 of aluminum forms upon the outer surface of the mandrel 54.

After a predetermined quantity of aluminum has solidified upon the mandrel 54, the mandrel 54 is withdrawn from the molten 1 159 and the aluminum is allowed to co l, hus forming a cup-shap d lank 40a.

After the blank .4041 has completely solidified, the mandral 54 is cooled to a temperature such that it shrinks l ghtly n size, ereby pe mitting y sep of t blank 4.0a from the mandrel 54.

Similarly to the blank 4. produced by the blowing technique, as described hereinbefore, the dip mold d ank 4.0 h s a side w ll so ewha ick r than i ot m 44a- A-ls somewh t simila t th pr ous cas the metal of the blank has a cast structure.

It is readliy apparent that a number of other molding methods may be employed to cast an aluminum blank having a bottom thinner than its side wall, and also having a cast structure. Some other techniques are die casting, permanent mold casting, shell mold casting, investment casting, and centrifugal casting, which may be used without departing from the spirit and scope of this invention. It is desirable, however, that the molded blanks be produced at a high rate, with the lowest possible per unit cost.

FIG- 9 sho a ng o d e gen al y d gna ed 1.10, within a die carrier 112. Both the gang 11 0 and the carrier 112 are mounted in a suitable hydraulic press. An annular ironing die 114 having a die aperture 116 is mounted the die carrier 112. The die aperture 116 is eham e ed s me hat at it jun ture wi h the upp r surface of the die 114.

Reciprocally mounted above the die 114, in axial aligne w t the di ape u 16, s a cylindrical r fin punch 120 having a lower end surfaee 122. The diameter o h pu c .12 s a proximate y h sam as the inside diameter of the blank 40. The Shape of the end surface 12. de e m n s to some e ent t e nd shape o t a t e 1 b formed d ay e fla ic lev or a cominat on o these s ape t pre e r d em odim nt shown in the drawings, a-fiat end surface 122 is used for producing flat=ended eontainers.

The u aped bl k 4 .is centere abo t e p ture 116 within an opening 123 in an annular blank holder 1 .4- f e r d, t lank h d r 1.24 m y be pa abl across a diameter for easier handling. The opening 123 has a diameter slightly greater than that of the diameter of the punch 120. A spaced series of guide holes 126 extends through the blank holder 124, adjacent the outer dg tu s 8 h ng han 1 and h ads 130, re threadably engaged to the die carrier 112 with the shank por ons ext n upw y h o gh th h les 126 in the blank holder 124 to prevent the blank holder from moving transversely relative to the die 114 and 1. hold h i g ng 11') og t er- The upper end of the punch 120 is attached to a piston rod 134, which in turn is actuated by a suitable power source such as an hydraulic cylinder, which is not shown. Upon actuation, the punch 120 moves downwardly, bringing the lower surface 122 into the blank 40 and into contact with the bottom 44 of the blank 40 (FIG. 10).

Continuing its downward movement, the punch 120 pushes the blank through the aperture 116 of the die 114 and forces the side wall 42 into contact with an ironing face 138. As the inside diameter of the ironing die 114 is slightly smaller than the outside diameter of the blank side wall 42, the side wall 42 is thinned and elongated as the blank 40 passes the ironing face 138.

While still being engaged by the ironing face 138, the blank 40 enters an annular ironing die 144 mounted in the die holder 112 below the die 114 (FIG. 11). The ironing die 144 has an ironing face 145 which is smaller than, and axially aligned with, the ironing face 138 of the die 114. A spacer plate 146 is disposedbetween the die 114 and the die 144 to produce a predetermined spacing between the respective ironing faces 138 and 145. The downward movement of the punch 120 forces the side wall 42 of the blank 40 past the ironing face 145, thereby reducing the thickness of and also elongating the side wall 42.

A-third ironing die 148, having an ironing face 149, is similarly mounted in the die holder 112 below the ironing die 144. A spacer 150. disposed between the ironing dies 144 and 148 produces a predetermined spacing between the respective ironing faces 145 and 149 thereof. As the punch 120 continues downwardly (FIG; 12), it carries the now partially heightened blank 40 into the ironing face 149 while the side wall 42 is still engaged by the ironing face 145 of the second ironing die 144.

Depending upon the spacings between the respective ironing faces, the side wall 42 may also still be engaged by the ironing face 138 of the ironing die 114 when it initially enters the ironing face 149 of the third ironing die 148. As it is moved downwardly, the side wall 42 is then disengaged from the ironing face 138 while still engaged by the ironing faces 145 and 149 of the ironing die 146 and 148 respectfully.

Further ironing of the side wall 42 is done by the ironing face 149 in order to reduce the side walls thickness and increase its length. The ironed container 152, finally formed, has an end 153 of substantially the same thickness as that of the end 44 in the blank 40 and a body 154, whose thickness is substantially less than the thickness of the side wall 42 of the blank 40. Preferably the thickness of the body 154 and the end 153 are substantially the same, although, where desirable, either may be thicker than the other depending upon the ultimate use of the container.

It is to be understood that, while the drawings show three ironing dies, fewer or more ironing dies may be used to produce any desired finished side wall height.

After passing through the third ironing die 148, the continuous downward movement of the punch 120 carries the formed container 152 through a conventional stripper, generally designated 156. The stripper 156 consists of a segmented flat annular ring 158 having a series of segments 160 adapted to slide radially within a recess 162 in the lower surface of the die holder 112.

The segments 160 are urged radially inwardly by springs 164 and are retained within the recess 162 by an annular fiat retaining ring 166, secured to the die holder 112 by screws 168. At the extreme inwardly position of the segments 160, the segmented ring 158 has a substan tially cylindrical inner surface 170 whose diameter is slightly less than the diameter of the punch 120, with a smoothly rounded upper edge 172 and a sharp lower edge 174.

As the formed container 152 is conveyed toward the stripper 156 by the punch 120, it contacts the rounded upper edge 172 of the segmented ring 158, forcing the segments 160 outwardly to allow the punch and container to pass through the ring. After the container 152 has passed through the ring 158, the springs 164 move the segments 160 inwardly against the punch 120. By suitable means (not shown), the punch 120 is then moved upwardly. During the upward movement of the punch 120, the upper rim 176 of the formed container 152 engages the sharp lower edge 174 of the segmented ring 158. This prevents any further upward movement of the container 152, thereby stripping it from the punch 120.

The cup-shaped one-piece finished container 152 (FIG. 13) has a generally smooth surfaced body 154 whose thickness is substantially the same as the end 153. In certain cases it may be desirable to have a body whose side wall is somewhat thicker than its end in order to give the container greater resistance to denting and deformation. This, of course, is easily accomplished by controlling the thickness of the side Wall 42 and bottom 44 of the blank 40 during molding and also the clearance between the punch and the ironing faces during the ironing operation.

As ironed, the end 153 of the container 152 has a generally as-cast structure such as is found in the molded blank 40. The structure will usually be fine grained, although the grain size will depend to a great extent upon the rate of cooling when the blank 40 is molded.

On the other hand, the body 154 will have an entirely different metallurgical structure than the end 153. This, of course, is due to the fact that the body has undergone a considerable degree of mechanical deformation during ironing. Thus, after ironing, the grain structure of the body 154 will have an elongated, cold-worked form with the grains being elongated longitudinally of the body 154 in the direction of ironing.

It is thought that the invention and many of its attenddant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction, and arrangement of the parts and that changes may be made in the steps of the method described and their order of accomplishment without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

I claim:

1. A method of manufacturing a cup-shaped one-piece metal container with a relatively thin side wall and bottom, comprising the steps of:

molding a cup-shaped blank from a pool of molten metal, the bottom and side wall of said blank having a predetermined thickness, the metal of said blank having an as-cast grain structure;

placing the bottom of said blank over and in alignment with a female ironing die assembly;

bringing a punch, aligned with said die assembly, into the cavity of said blank, said punch fitting snugly within said blank; and

forcing said blank through said die assembly whereby the side wall of said blank is elongated and substantially reduced in thickness in each die of said ironing die assembly Without any substantial change in the thickness of said bottom.

2. The method set forth in claim 1 wherein the thickness of said blank bottom is different from the thickness of said blank side Wall.

3. The method of claim 1 wherein said metal is an aluminum alloy.

4. The method of claim 1 wherein said blank is molded by immersing a cooled mandrel into said pool of molten metal whereby a layer of metal freezes upon said mandrel and then removing the coated mandrel from said pool of molten metal, said mandrel having said cup-shaped blank formed thereon.

5. The method of claim 4 wherein the wall of said mandrel is cooled at a faster rate than the bottom of said mandrel while said molten metal is solidifying upon said mandrel.

6. The method of claim 1 wherein said die comprises at least 2 spaced ironing dies.

7. A method of manufacturing a cup-shaped one-piece metal container with a relatively thin side wall and bottom, comprising the steps of:

placing a closed end vented mold having a cup-shaped cavity above and in contact with the surface of a pool of molten metal;

introducing a gas bubble into said molten metal substantially directly below said die cavity whereby said assembly bu ble is int 211 5 s made o expand in sa dis savi y thus lini g S id cav y with meta pe m ins said ms a i h said dis av ty t s li y;

em ng s id di qm sa d poo f mo en me al and withd aw ng a cup-s aped vbl amk fro said dis y, the ,mdal pr ai si l n ha ing an as-n g in strucim plasz g the bottom of said blank .o r (a d i l gn en with a female ironing die assembly;

brin ng a punch, .a i sd wi s d ass bly, in o e cavity of said lank, s id pu ch fitt g nugly within aid bl nk; an

i r in s d bl n t roug a i on ng d a sembly whereby h s de wal f s d bl nk is e19ns d an su a tia ly educ n t ick ss wi h ut any stantial ehange in the thickness of said bottom.

8. The method set forth in claim 7 wherein the ,thickness of said blank bottom is difierent from the thickness of said blank side wall.

9, The method of claim 7 wherein said metal is an aluminum a l y.

10, The method of claim 9 wherein said gas is van oxidizer.

11, The method of plaimfi wherein said blank comprises outer layers of aluminum oxide and an inner layer of um num- 112, The method of claim 9 wherein said ironing die asm y somp i ss a lea t two p c d i References Cited U T D TA ES ATENTS 303,607 3/118184 Arencibia 22*210 1,925,823 9/ 1933 Singer 72-?348 1,931 210 10/ 193 3 Steinacher. 2,327,956 8/1 9143 Slate: 72-4-3 47 3, 184,296 5/1955 Schaich.

3,184,940 5/ i965 Spprck 72-348 J HN F- MP EL ri y Examine 20 GEORGE E. LAWRANCE, Examiner.

.P M. COHEN, A sis ant Examin r 

1. A METHOD OF MANUFACTURING A CUP-SHAPED ONE-PIECE METAL CONTAINER WITH A RELATIVELY THIN SIDE WALL AND BOTTOM, COMPRISING THE STEPS OF: MOLDING A CUP-SHAPED BLANK FROM A POOL OF MOLTEN METAL, THE BOTTOM AND SIDE WALL OF SAID BLANK HAVING A PREDETERMINED THICKNESS, THE METAL OF SAID BLANK HAVING AN AS-CAST GRAIN STRUCTURE; PLACING THE BOTTOM OF SAID BLANK OVER AND IN ALIGNMENT WITH A FEMALE IRONING DIE ASSEMBLY; BRINGING A PUNCH, ALIGNED WITH SAID DIE ASSEMBLY, INTO THE CAVITY OF SAID BLANK, SAID PUNCH FITTING SNUGLY WITHIN SAID BLANK; AND FORCING SAID BLANK THROUGH SAID DIE ASSEMBLY WHEREBY THE SIDE WALL OF SAID BLANK IS ELONGATED AND SUBSTANTIALLY REDUCED IN THICKNESS IN EACH DIE OF SAID IRONING DIE ASSEMBLY WITHOUT ANY SUBSTANTIAL CHANGE IN THE THICKNESS OF SAID BOTTOM. 